Apparatus for electrolytically depositing metal on metal tubes



s sheets-sheet 1 Dec. 2 1930.

F. G. MARTIN ET AL APPARATUS FOR ELECTROLYTIGALLY DEPO SITING METAL 0NMETAL TUBES Fil ed Sept. 29. 1927 2 193 F. G. MARTIN E A? 3 I APPARATUSFOR ELECTROLYTIGALLY DEPOSITING METAL 0N METAL TUBES Filed Sept; 29,1927 I Shets-Sheet 2 1930. M RTINEHL 1,783,885

APPARATUS FOR ELEGTROL YTICALLY DEPOSITING METAL ON IIETAL TUBES '1 a fA 1 6 Filed Sept. 29, 1927 3 Sheets-Sheet .5

- Patented Dee 2, 1930 PATENT OFFICE runners enmsna'w marm mm WILLIAM.BAKSAY, or Bmxmuman, ENG AND,

assrenons T0 J. STONE & company LIMITED, or nnrrronn, ENGLAND APPARATUSFOR ELECTROLYTICALLY DEPOSITING METAL ON TUBES Application filedSeptember 29, 1927, Serial No. 222,829, and in Great Britain Aprilj22,1927.

This invention comprises improvements in apparatus for electrolyticallydepositing metal on metal tubes or tubular articles and suchimprovements are particularly applicable for the coating of condensertubes, superheater tubes and so on, with the object of rendering themincorrodible when in use. The lining of the interior of brass tubes ofsmall diameter with a coating of chromium is most advantageous when suchtubes are intended for use in condensers for marine and other work, inwhich it is of importance to avoid leakage of salt water or othercorrosive liquid, into the steam generator system.

The apparatus involves the employment of a flexible anode which iscentred andtensioned within the bore of the tube. In this way, it isrendered possible to avoid contact of the anode with the interior of thetube to be coated, whilst preserving a free annular number of tubes ofconsiderable length and small bore and it is important, from thepractical and commercial points of View, to provide methods and meansadapted for enabling large numbers of tubes to be reliably coated in aneflicient and fool-proof man- 'ner without necessarily involving theemployment of skilled labour. Important objects of these improvementsinclude the provision of methods and means calculated to render itpossible for relatively unskilled labour to mount large numbers of smallbore tubes with their anodes properly centred within them andto.carry'out the electrolytic coating thereof without loss of workingtime and in a thoroughly reliable manner; The said objects also includethe provision of advantageous forms of. anode and means for enablingsuch anodes to be quickly inserted and ten'sioned within tubes to becoated. Finally, the said objects include the provision of means forenabling end: portions of the tubes to be coated externally whilst thebores be descn ing and holding the tubes and for the mounting andtensioning of anode devices within such tubes whilst leaving the boresand ends of the tubes perfectly free for circulation of electrolyte andescape of gases. The flexible anode may be composed of a number of metalstrands or wires which are subjected to compression so that theinterstices within the stranded or rope-like anode disappear and maximumcross-sectional area ofconductor metal is obtained for a given diameterof flexible anode. The flexible anode may comprise a non-flexible endportion, for the latter facilitates the threading of the anodes throughthe tubes and the mounting and fixing of devices adapted for receivingthe pressure to be applied by the tensioning means. In order that thelabour employed shall not be "required to make sk ilful tensioning adforproducing the tension and to provide means for enabling thesprings to beapplied to the anodes so that allwill have a sufiicient and more or lessuniform tension, although positively adjustable tensioning means may beemployed. Theframing is adapted for supportingthe tubes with their endportions freely exposed, and ring-form or tubular anodes may besuspended or supported around justments, it is convenient to employsprings suchend portions whereby the latter will re ceive an externalcoating at the same time that the bores are coated. These end portionsare those which are jointed in the condenser plates and receive fixingferrules or the like. The externalcoatings on such end portions protectthem against corrosion.

In order to enable the invention to be readily understood, reference ismade to the accompanying drawings illustrating suitable examples ofelectrolytic bath apparatus adapted for carrying out the coating oftubes in accordance with these improvements, in which drawings Figure Iis a vertical section of a cylindrical tank containing a framesupporting tensioned anodes and tubes to be coated.

tubes a.

Figure 2 is a plan of Figure 1.

Figure 3 is a vertical longitudinal section of one end portion of adeeptrough-like tank containing a modified construction of frame forsupporting tensioned anodes and tubes.

Figure 4 is a vertical transverse section of Figure 3.

Figure 5 is a cross section of an advantageous construction of anode.

Figure 6 is a sectional elevation of anode gripping means which may beused in some circumstances.

Figure 7 is a sectional elevation of a detail applied to the end of atube.

Referrin to Figures 1 and 2, the tubes a to be plate I. withan'internal'coating such as chromium, the internal anodes b, andexternal ring anodes c, 0 are all supported in a frame comprising aseries of rings d e f g and 72/. As the tubes tobe coated may be ofgreat length, such as eighteen or twenty feet or more, and the tank ofcorresponding depth, only the top and bottom portlonsof the tank andframe are seen in F igure 1, the middle portion being absent as will beunderstood from the lines indicating a break in Figure 1.

In a complete or unbroken structure, the frame comprises other ringsbetween the rings 7 and 9 such other rings giving support and guidanceto the middle ortions of the tubes to be coated. The num er of suchinterme dizte rings will depend upon the length of the tu es.

The rings 7 and g supporting the tubes, and the intermediate ringsaforesaid, are formed with aligning perforations to receive the Thetubes may be secured in the ring 7 by clamping means such as splitcollets of which one example is shown at the left hand side of Fi ure 1.This split collet a is inserted u wardly into a ta ered hole in the ringan is screw threade to receive a nut afi. y tightening the nut a uponthe ring f the collet a is drawn upwardly in the tapered hole and isthereby caused to grip the tube passing through it. The tubesa may besecured'in the ring 9 instead of in the rm f, or they may be secured inthe ring 9 as wefias in the ring 7. For example, and as seen to theright hand side of Figure 1, the tubes may be secured in the ring 9 bymeans of split tapered collets a 'which re uire merel to be pressed downinto tapere holes in t e ring ii in order to grip the tubes, the weightof the tter operating to increase the security of the gripping as willbe ap arent.

The rings 6 and k are a apted for supporting the anodes b concentricallywithin the tu es a and for this purpose are formed with perforationsaxially aligned with those of the rings f and g. The holes in the bottomring it are tapered to receive conical insulator busheslt' in which thelower ends of the flexible anodes b are engaged or fixed. Thus, thelower ends of the anodes may be knotted or pressed to have a button-likeformation which cannot be drawn through the bush h. The perforations ofthe ring 0 are large enough to receive insulator bushes e which servefor the guidance of the upper ends of the anodes b and also for theseating of tensioning sprin s as hereinafter described. The ring 05 isormed on itsouter periphery with radially extending clips d which can betightened on to the upper ends 6 of the anodes and which can also servefor clipping and suspendin the rods 0 of the external anodes hereina erdescribed.

The flexible anodes b are advantageously constructed from lengths ofhigh conductivity copper wire rope drawn-with a covering of lea In orderto get rid of interstices and to obtain a maximum cross sectional areaof conductive metal with a 1'0 e of given diameter, the said rope may be'ghly compressed so that the strands acquire more or less the sectionseen in Figure 5, the lead covering being indicated by b in this figure.Alternatively steel anodes, not requiring a covering of lead, may insome cases'be employed for the coating of large tubes.

The frame comprising the rings d e f g ,h is constructed by mountingthese rings on long bolts z in the following manner:--The lower ends ofthe bolts are rounded to serve as feet and are furnishedjust above suchfeet with abutments, which may take the form of nuts 2'. The ring itrests upon the abutments or nuts 2" and the superposed rings 9 e f (Zare spacedapart on the bolts by spacer sleeves Z. The top ring d, whichserves as a bus bar for the anodes, must be insulated from the bolts 2',sleeves Z, and top securing nuts m, and insulator bushes and washers dare provided for this purpose. The top ring d may be fitted with aterminal post d for connecting itwith the positive terminal of a sourceof current.

. Uther means may be employed for mounting the rings with appropriatespacing. For example, the sta. be tsz' may be screw threaded throughoutt eir length, or over predetermined portions of their length, and nutsscrewed on to the rods then serve for supportingr the rings at thedesired distances apart.

he cup-shaped tops of the bushes e serve for seating, as aforesaid,springs n which are coiled around the upper end portions of the anodesand press upwardly against collars n adj ustably fixed on the anodes-asby the set screws n. The collars n are set so that the resultingcompression of the springs is sufficient for tensioning the flexibleanodes b and keeping them taut and concentric within respective tubes a.v v

The collars a may be applied in the manner shown in Figure 6 which hasbeen found to be a convenient and practical method; In this constructionthe anode is shown as having a portion of reduced diameter forming agroove in which is placed a split collet n having a tapered externalsurface adapted to be engaged by the tapered internal surface of acollar n. The collar is held down against the pressure of the spring,whilst the halves of the collet are placed in position and is thenreleased to engage the colletand the anode is thus tensioned as will bereadily understood. v Or the tensioning of the anodes maybe effected byproviding a screw threaded portion at theupper end of each rod andengaging this portion by a fly nut. Suitable expedients, such' as theprovision of vertical grooves in the anode engaged by fixed parts oftheapparatus, may be adopted for preventing turning of the rod during thetensioning adjustment as such turning may be detrimental to thestructure of a stranded anode.

A frame constructed as hereinbefore described is loaded with tubes (1and anodes 6 prior to its insertion into the electrolytic bath in thebank is. The frame may be laid on its side on a bench and the tubes amay be pushed through the perforations of the ring h and then throughthe perforations of the ring 9 and alsothrough the perforations of anyintermediate rings until their ends pass through the perforations of thering f. The distance of the ring 7 from the ring 9 is' adjusted sothatit is less than the length of the tubes to be plated. The tubes aare inserted so that they project at each end a suitable distance beyondthe rings f and g as shown in Figure 1. When in proper endwise position,the tubes are secured by the collets a or a hereinbefore described. Theflexible anodes have now'to be passed through th'e perforations in thering h and through the tubes (1 placed in position in' the frame. Inorder to assist in threading the anodes through'the small bores of thetubes a, the upper end portion 12 of each anode may be ofa rigid ornon-flexible character such as may be obtained by the provision of asteelsleeve passed over the end of the copper rope. The

latter may be opened out and-soldered at' its I end, whilst the leadcoating is soldered or burnt on to the steel sleeve in order to preventthe electrolyte (when plating with chromium) from coming into contactWlth the copper conductor core. When the ends b of the anodes b havebeen passed through the tubes a they-are passed through theperforationsof the ring 6 and the coned insulator bushes on theiroppositevends take a seating in the ring h. The bushes e, springs n, andcollars n are now passed on to the rigid ends. of the anodes, the bushes6'- being seated in the ring 6 and'the collars n' being adjusted toobtain spring pressure as explained above. The bus bar clips d arefinally tightened on i the anodes.

One of the stay bolts {is formed at thetop with'an extension 0 whichserves for connect-v ing the frame with the negative terminal of thesource of current. As the tubes 0 are in good electrical contact withthe rings f and g and with intermediate rings of the frame as aforesaid,the frame itself makes a very satisfactory cathode connection. The anodeparts are all insulated from the frame as already explained.

, The frame may be suspended from thetank by projections or hooks on theframe engagin" with the top of the tank..

f only the bores of the tubes a had to be plated, the, loaded framewould be ready for being lowered into the bath. However,'it' is bar' das aforesaid, and these rods being formed or fitted with ring anodes cand 0 which encircle the endv portions of the tubes projecting beyondthe rings 7 and 9 respectively. The rods 0 for the main portion of theirlength are provided with insulating tubes of suitable material such asglass orvulcanite, but the metal of the rings a c is exposed to theelectrolyte. The rods 0 may ,be of steel or other suitable material andthe rings 0 0 which are made of copper covered with lead are securedthereon in any convenlent manner. The rod 0 should be 1nportions of therods 0 conveniently enga e in notches in the peripheries of the rings eg.

The flat frame employed in the modification in Figures 3 and 4,comprises end vertical bars such as p supporting horizontal bars f g'sulated by any suitable means. The straight j and h which correspondwith the rings bear- T ing the same reference letters in Fi ure 1. Thetubes aware supported and secure in the bars f and g in the same manneras described with reference to the ring construction in Figure 1. Thelower ends of the anodes may be flattened, as shown, and coveredwith-lead buttons 9 which bear against the coned insulator bushings h. Atop bar 1' bolted to the vertical end bars p is of hollow formation and.

is fitted with a terminal r for the negative connection. The insulatedanode rods 0 pass through perforations in the bar r and the ends of theflexible anodes I) pass through in-- sulator bushes r inserted in otherperfora-. tions in the bar 1'. The external anode rods 0 7 aresuspendedfrom, and electrically connected with, a copper bus bar .8 bymeans of binding screw devices as shown, the bus bar 8 resting uponflanges of the bushes 1" and beingthereby insulated from the bar 1'.Screw threaded sleeves t are secured to the upper ends of the anodes band screw into nuts t resting upon the bus bar 8. The flexible anodes bare tensioned by adjustment of the nuts t as will be a parent fromFigure 3. The lower ring ano e a may be formed by bending the rod 0, thevertical ortion of which in the case of chromium plating should have asteel covering, after the latter has been inserted through the bars 7and g, or it may be detachably mounted on the rod a like the upperanodering c in Figure 3.

It is to be understood that the means shown for the external plating ofthe ends of the tubes is merely one example of con: struction, it beingadvantageous to employ instead of the rings 0, c tubular anodesextending over the ends of the tubes and of a length approximately equalto the length of external plating-it is desired to apply to the tube.Also it is contemplated that ring or tube anodes may be'supported to thecentrail anodes 6 thereby dispensing with the ro s a. v

The hollow top bar 1' with its end walls Wand side walls 1* forms a hoodat the top of the frame. Baflies may be provided in the hood and gasescollecting during the electrolytic process may be drawn off through aconnection 7- by a fan so that they are discharged where they can haveno harmful effect on the workmen. A door may also be arranged in thehood through which the frame is adapted to be lowered and lifted. Ifdesired, a similar hood could be provided for the constructionillustrated in Figures 1 and 2.

To-prevent 'undue rise of temperature in the bath during the process acooling pipe or coil such as 24. Figures 1 and 2, may be provided forthe circulation of cooling fluid.

As shown in Figure 7 a small hollow vulcanite cap a may be fitted on theoutside of each tube at its ends, these plugs being formed with holes wfor the passage of the anodes b and with small holes w in theircylindrical portions to permit of the circulation of the electrolyte, ithaving been found that the provision of these caps enhances and improvesthe coating of the tubes at their ends. Although the cap is shown vasmerely gripping the tube any suitable means may be employed forconnecting the caps to thetubes.

The cross sectional area of the flexible anodes is'usually such thatthey will carry the deposition current without serious drop of potentialat the lower end when current is .led into the upper end only. Acertaindrop of: potential is inevitable but is compensated by the fact that theelectrolyte is more concentrated at the lower ends of the tubes to becoated. If desired, current maybe supplied to both ends of the flexibleanodes b, in which case the lower'ring or tube anodes o maybe supportedupori' the lower -bus bar which would then be used, or they may besupported upon the lower end portions of the flexible anodes b.

By the hereinbefore described method and apparatus it is possibleuniformly to coat with chromium large numbers of brass condenser tubesof the usual diameter and bore and of lengths up to eighteen and twentyfeet or more. No particular degree of skill is necessary for themounting of the tubes and anodes in the frames, for uniformity ofpositioning of the tubes and of tensioning of the anodes can be readilyattained with ordinary care. Also, no particular degree of skill isrequired for supervising the electrolytic process, the degrees ofcurrent strength and electrolyte concentration and the plating periodand bath temperature, being all prescribed for a given job. The detailsof construction will, of course, be modified to suit the plating oftubes of lengths, diameters and bores.

Before commencing the electrolysis it may be necessary to effect awashing or pickling of the tubes as byv dipping them in waste chromicacid with or without an addition of sulphuric acid. Also after removalfrom the electrolytic bath it is necessary to wash the tubes and frameto free them of chromic acid. The tubes, being securely mounted in theframe, are readily lowered into and removed from washing or picklingbaths and are conveniently disposed for the running of cleaning brushessuch as wire brushes, through their bores or for treatment by water jetsand so on. The conveyance of the frame and tubes from and to the varioustreatment tanks may suitably be effected by lifting means of anconvenient form. After removal from t e frame, the washed tubes may bestacked to drain and dry. Whilst the coating of one batch of tubes isproceeding, the workman is employed in loading a second frame with tubes1n the manner described, this second batch being introduced into thebath when the first batch is finished, as will be readily understood.

It will be noted that in securin the tubes in the frame and tensioning te anodes therein as above described, the tubes are not subjected toaxial compression so that there is no influence tending to bend anddestroy the straightness of these long thin tubes of small diameter. Onthe other hand, the said tubes being su ported each in a number ofaxially aligne perforations'there is a positive tendency to preservetheir straightness. Also, the tubes and flexible anodes being supportedin a-truly vertical position and the anodes being tensioned, there is notendency for the anodes to sag or bend and to lose that concentricity oraxial alignment which is important for the attainment of uniform andreliable coatings.

When brass. tubes are to be coated with different chromium a loadedframe may be lowered into the bath before the current is switched 1 on,the electrolyte acting preliminarily as a frame is lowered into thebath.

We claim s Electrolytic apparatus comprising a frame having (and membersand a series of intermediate members, said intermediate members beingperforated to receive the tubes to be coated, gripping devices arrangedin said perforations and ada ted for fric-. tionally engaging saidtubes, exible anodes supported concentricall within the tubes betweensaid end mem ers and tensioning means operative between one of said endmembers and said anodes for tensioning said anodes.

2. Electrolytic apparatus comprising a frame composed of longitudinals,end members, and a series of intermediate perforated members, spacersfor distancing said intermediate members along saidlongitu'dinals,

collets associated with said intermediate members for frictionallyengaging tubes guidingly inserted throughthe perforations of saidmembers flexible anodes supported by saidtopan bottom membersconcentrically within said tubes and tensioning means operative betweenone of said end members and said anodes.

3; Electrolytic apparatus comprising a frame composed of longitudinals,end members, and a series of intermediate perforated members, grippingmeans associated with said intermediate members adapted for frictionallyengagin tubes guidingly inserted through the per orations of saldmembers, the uppermost and lowermost members of the intermediate seriesbeing so disposed that the ends of the tubes project beyond them,external'anodes adapted to surround said projecting ends of the tubes,internal flexible anodes disposed within said tubes and extended betweensaid end members, and

tensioning means operative for tensioningv said internal anodes. Y -4.In electrolytic apparatus for carrying out processes of the kindreferred to, the

combination of a tank, a frame adapted to y be supported within saidtank and comprising top and bottom members and intermediate perforatedmembers, gripping devices associated with one of said mtermediatemembers and adapted for frictionally engaging the tubes, flexible anodesmounted concentrically within said tubes, tensioning means for saidanodes, external anodes adapted for coatin the ends of said tubes, andinsulated con uctors supporting said *externalanodes.

5. In' electrolytic apparatus for carrying out p o the kind referred to,v the combination of a frame comprisin end rings and a series ofperforated interme iate rings,

grippin devices associated with one of said interme iate rings forfrictionally engaging tensioning means operative between an end ring andthe upperparts of said anodes.

6. In electrolytic apparatusfor carrying out processes of the kindreferred to, the combination of a tank, a cathode frame comprising endrings and a series of intermediate perforated rings, gripping devicesassociated with one of said intermediate rings adapted for supportingtubes inserted into the perforations of said intermediate rings,flexible. anodes arranged between the top and bottom rings and withinthe tubes, abutments on said anodes, compressionsprings between an endring and said abutments, and electrical terminal means for said anodeand said frame.

7. In electrolytic apparatus for carrying out processes of the kindreferred to, the combination of a tank, a cathode frame comprison saidanodes, compression springs between an end ring and said abutments, aterminal devlce connected wlth'sald anodes, insulated conductorssuspendedfrom said terminal de- -v1ce, anodes supported by saidconductors and adapted to surround the ends of the tubes, and anelectric terminal for said cathode frame.

8. Apparatus forcarrying out processes of the kind referred to,comprising a-tank, a

frame adapted for vertically supporting a' number of tubes by slidinglyengaging the latter at several points along their length, flexibleanodes mounted in said frame and concentrically within said tubes,tensioning means forsaidanodes, and a hood device surmountin said anodesand adapted for the discharge 0 gases evolved during the process. 9.Apparatus for carrying out processes of .the kind referred to,comprising a tank, a frame adapted for vertically supporting a number oftubes by sildinglyengaging the latter'at several points alongtheirlength, flexible anodes mcungedcon ntrica wi said tubes,tensioningi'iibans for sai anodes and external anodes surrounding theends of said tubes. 1

10. Electrolytic apparatus com rising a frame for supporting a number 0tubes by slidingly engaging the latter at several points between theirends, and tensionin means for anode rods extended through sai tubes. 1

11. Electrolytic. apparatus comprising acathode frame composed ofa'serie's of horizontal members, accuratel aligned holding devicesassociated with sai members mfor vertically supporting a number of tubesat several points between their ends, flexible anodes mountedconcentrically within said tubes, and tensioning means for said anodes.

12. In electrolytic apparatus, the combination of a tank, a frameadapted to be supported within said tank and com rising intermediatemembers, accurately ahgned holding devices associated with saidintermediate members for sup orting a number of tubes between theirends, end members adapted to support flexible anodes concentricallywithin sai tubes, and tensioning means for said anodes.

13. In electrolytic apparatus, the combination of a tank, a frame adated to be supported within said tank an comprising a series ofhorizontal members, accurately aligned holding devices associated withsaid members for vertically supporting a number of tubes at severalpoints between their ends, spacers for separating said frame members,end members on said frame for su porting flexible anodes within saidtubes, and tensioning means operative between said end mem bers and theanodes. p

14. In electrolytic apparatus, the combination of a tank, a frameadapted to be supported within said tank and comprising top and bottomrings and a series of intermediate 7 perforated rings, spacers for saidrings, ac-

curately aligned holding devices associated with said intermediaterings, flexible anodes supported between said top and bottom rings, andtensioning means operative between said frame and the anodes.

FRANCIS GRIMSHAW MARTIN. WILLIAM RAMSAY.

